Preparation method of lead-sulfur group quantum dot material

Abstract

The invention relates to a preparation method of a lead-chalcogenide quantum dot material, simultaneously protects the lead-chalcogenide quantum dot material prepared by adopting the method and application of the material, and belongs to the technical field of compound semiconductor materials. The preparation method specifically comprises the following steps: dissolving lead halide and a chalcogenide precursor in N, N-dimethylformamide; the preparation method comprises the following steps of: adding the lead sulfide into N, N '-dimethylformamide to form a precursor solution A, dissolving oleylamine into toluene to form a precursor solution B, adding the precursor solution A into the precursor solution B, adding ethanol after the reaction is finished, and centrifugally separating to obtain the lead-sulfur group quantum dot with the oleylamine and halogen co-coordinated, the quantum dot can generate the lead-sulfur group quantum dot in which oleic acid and halogen are co-coordinated through ligand exchange. The lead-sulfur group quantum dot material disclosed by the invention has the advantages of simple preparation method and high yield, and has the characteristics of adjustable material wavelength, high luminous efficiency and the like when being used in a luminescent device.

Description

Technical Field

[0001] The invention relates to a method for preparing a lead sulfide quantum dot material, and at the same time protects the lead sulfide quantum dot material prepared by the method and the application of the material, belonging to the technical field of compound semiconductor materials. Background Art

[0002] Lead sulfide quantum dot materials of group IV-VI have the advantages of large Bohr radius, significant quantum confinement effect, and solution processing. Among them, lead sulfide quantum dots and lead selenide quantum dots have a wide wavelength adjustment range in the infrared band (800-1500, 1200-4100nm), and are currently one of the most promising infrared luminescent materials.

[0003] At present, the most mainstream method for preparing lead sulfide quantum dots is hot injection. Taking lead sulfide quantum dots as an example, at a temperature of 75-150°C, highly active hexamethyldisilathione is rapidly injected into a hot lead oleate solution as a sulfur source to react and form lead sulfide quantum dots. However, in this preparation method, the quantum dot nucleation process is completed within a few seconds. In large-scale preparation, the hot-injected hexamethyldisilathione has already nucleated locally before the reactants are evenly mixed, resulting in poor batch consistency. Most other traditional synthesis methods of lead sulfide quantum dots require high temperature (75-150°C) and inert gas protection, and some highly active and smelly sulfide precursors used must be stored in a glove box. Generally speaking, preparation methods that do not require heating and inert atmosphere are more conducive to large-scale preparation. In recent years, the literature has reported a method for directly preparing semiconductor lead sulfide quantum dot ink at room temperature (Nat. Commun., 2019, 10, 5136), in which I was directly prepared in N,N'-dimethylformamide. - Ion-coordinated lead sulfide quantum dots. - Ion-coordinated lead sulfide quantum dots have strong charge transport capabilities and can be directly used to prepare photovoltaic devices, but their luminescence efficiency is low and they are not suitable for use as luminescent materials. With the increasing demand for efficient near-infrared luminescent materials, it is urgent to develop new methods for large-scale preparation of efficient luminescent lead sulfide quantum dots. Summary of the invention

[0004] In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a method for preparing a lead sulfide quantum dot material with high efficiency luminescence, which is characterized by being simple, suitable for large-scale preparation, and having good batch consistency.

[0005] The present invention provides a method for preparing a highly efficient luminescent lead chalcogenide quantum dot material, wherein all steps are performed at room temperature and without the need for inert atmosphere protection. The specific steps are as follows:

[0006] (1) Preparation of precursor:

[0007] Lead halide and chalcogenide precursor are dissolved in N,N'-dimethylformamide, wherein the molar ratio of lead halide to chalcogenide precursor is 1:1 to 3:1, and a precursor solution A is formed after sufficient stirring. The concentration of the chalcogenide precursor in the precursor solution A is 0.05M to 0.5M, preferably, the concentration is 0.1M to 0.3M.

[0008] Oleylamine and toluene are mixed and stirred sufficiently to form a precursor solution B, wherein the volume fraction of the oleylamine in the precursor solution B is 5% to 100%; or oleylamine is directly used as the precursor solution B.

[0009] (2) Preparation of lead sulfide quantum dots:

[0010] The precursor solution A is quickly added to the precursor solution B, and the solution is kept stirred vigorously. The reaction time is 5-120 minutes. After the reaction is completed, an excess of ethanol is added, and the solid is separated and purified to obtain the lead sulfide quantum dots coordinated by oleylamine and halogen.

[0011] (3) Ligand exchange:

[0012] Add oleic acid and n-hexane to the lower solid obtained in step (2), stir and mix quickly, let stand at room temperature for 6-12 hours, separate and purify, and obtain lead sulfide quantum dots coordinated by oleic acid and halogen;

[0013] In step (1), the preparation method of the precursor solution A is as follows: after mixing the lead halide and the chalcogen precursor with N,N'-dimethylformamide at room temperature, the mixture is stirred sufficiently to form a clear and transparent precursor solution A.

[0014] In step (1), the lead halide is selected from lead chloride, lead bromide or lead iodide. When lead chloride is used, additional dimethyl sulfoxide needs to be added to dissolve it. Lead bromide is the most preferred.

[0015] The chalcogen precursor described in step (1) has a structure as shown in formula A:

[0016]

[0017] In formula A, the E is selected from sulfur and selenium; the R 1 , R 2 , R 3 , R 4 are independently selected from one of hydrogen, substituted or unsubstituted C1-C20 alkyl, substituted or unsubstituted C6-C60 aryl, and the substituted substituent is selected from one of halogen, C1-C10 alkyl, and C1-C10 alkoxy;

[0018] Preferably, the R 1 , R2 , R 3 , R 4 two of which are selected from hydrogen;

[0019] Preferably, the R 1 , R 2 At least one of them is selected from substituted or unsubstituted C6-C60 aryl, wherein R 3 , R 4 At least one of them is selected from substituted or unsubstituted C6-C60 aryl, and the substituted substituent is selected from one of halogen, C1-C10 alkyl, and C1-C10 alkoxy;

[0020] More preferably, the R 1 , R 2 One of them is selected from substituted or unsubstituted C6-C60 aryl, and the other is selected from hydrogen, said R 3 , R 4 One of them is selected from substituted or unsubstituted C6-C60 aryl, and the other is selected from hydrogen, and the substituted substituent is selected from one of halogen, C1-C10 alkyl, and C1-C10 alkoxy;

[0021] More preferably, the R 1 With R 3 is a C6-C60 aromatic group, wherein R 2 and R 4 A hydrogen atom.

[0022] When preparing lead sulfide quantum dots, the sulfide precursor described in step (1) is a thiourea derivative selected from N,N'-diphenylthiourea, N,N'-di-n-butylthiourea, and N,N'-di(4-methylphenyl)thiourea; preferably, the sulfide precursor described in step (1) is selected from N,N'-diphenylthiourea.

[0023] When preparing lead selenide quantum dots, the chalcogenide precursor in step (1) is selenourea and its derivatives selected from selenourea and N,N'-dibutylselenourea;

[0024] In step (1), as the volume fraction of oleylamine in the precursor solution B increases, the emission wavelength of the obtained lead sulfide quantum dots red-shifts.

[0025] In step (2), the separation and purification process specifically includes adding excess ethanol to the quantum dot solution to precipitate the quantum dots, and after centrifugal separation, the upper layer is a colorless clear liquid and the lower layer is a black solid. After the supernatant is removed, the lead sulfide quantum dots coordinated by oleylamine and halogen are obtained.

[0026] In step (2), after the precursor A solution is added to the precursor B solution, the solution is kept stirred vigorously, and the reaction time is 5-120 minutes. The longer the reaction time, the narrower the band gap of the obtained lead sulfide quantum dots, and the redder the absorption and emission wavelengths.

[0027] The volume fraction of oleic acid in the n-hexane solution in step (3) is 10% to 30%.

[0028] In step (3), the separation and purification process specifically includes adding excess ethanol to the quantum dot solution to precipitate the quantum dots, centrifuging, and discarding the supernatant. The black solid at the bottom layer is the lead sulfide quantum dots coordinated by oleic acid and halogen.

[0029] The present invention also protects the lead chalcogenide quantum dot material prepared by the method of the present invention, which has adjustable near-infrared emission and high luminous efficiency. The lead chalcogenide quantum dot material of the present invention can be used in light-emitting devices.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The operation is simple. The preparation process does not require heating or inert atmosphere. The required equipment and materials are cheap. Large-scale preparation can be achieved by simply increasing the amount of all reactants and solvents. Gram-level lead sulfide quantum dots can be prepared in a single batch, and the batch consistency is high, which is suitable for large-scale preparation.

[0032] (2) All precursors are stable in air and do not require inert gas protection or special equipment for storage;

[0033] (3) The resulting lead sulfide quantum dots are coordinated by oleic acid and halogen, achieving efficient passivation of the lead sulfide quantum dots, with a photoluminescence quantum yield (PLQY) of up to 45%; BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Absorption spectra of lead sulfide quantum dots prepared using different lead halides provided in Examples 1-3.

[0035] Figure 2 A transmission electron micrograph of lead sulfide quantum dots provided in Example 2.

[0036] Figure 3 The X-ray diffraction pattern of the lead sulfide quantum dots provided in Example 2 and the standard diffraction peaks of lead sulfide (PDF#05-0592).

[0037] Figure 4 This is an absorption spectrum diagram of the lead sulfide quantum dots provided in Example 4 at different reaction times.

[0038] Figure 5Absorption spectra of lead sulfide quantum dots prepared using different chalcogenide precursors provided in Examples 2 and 5-6.

[0039] Figure 6 Absorption spectra of lead sulfide quantum dots prepared using lead bromide and N,N'-diphenylthiourea in different ratios as precursors provided in Examples 2, 7-8, wherein the molar ratio of lead bromide to N,N'-diphenylthiourea is 1:1, 2:1 and 3:1.

[0040] Figure 7 Absorption spectra of lead sulfide quantum dots prepared with different concentrations of N,N'-diphenylthiourea provided in Examples 2, 9-10. The molar ratio of lead bromide to N,N'-diphenylthiourea is fixed at 2:1, and the concentration of N,N'-diphenylthiourea in precursor solution A is 0.1M, 0.2M and 0.5M.

[0041] Figure 8 Absorption spectra of lead sulfide quantum dots prepared using different precursor solutions B provided in Examples 2 and 11-14. The volume fraction of oleylamine in precursor solution B is increased from 10% to 100%, and 100% means that pure oleylamine is used as precursor solution B.

[0042] Fig. 9 The absorption and emission spectra of lead sulfide quantum dots before and after ligand exchange provided in Example 15.

[0043] Fig.10 This is the absorption spectrum of the lead selenide quantum dots provided in Example 16.

[0044] Fig.11 These are photos of the lead sulfide quantum dot amplification reactions provided in Examples 15 and 17-20.

[0045] Fig.12 Absorption and emission spectra of lead sulfide quantum dots prepared by different scale-up reactions provided in Examples 15, 17-20.

[0046] Fig.13 Schematic diagram of the QD-LED device structure provided in Example 21.

[0047] Fig.14 The luminous spectrum of the QD-LED provided in Example 21 at different currents and the graph of the change of light power with current. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and are not used to limit the scope of the present invention.

[0049] Embodiment 1:

[0050] Step (1): Weigh 2 mmol of lead chloride and 1 mmol of N,N'-diphenylthiourea, add them into 3 mL of dimethyl sulfoxide and 2 mL of N,N'-dimethylformamide, and stir thoroughly to form a precursor solution A;

[0051] Add 1 mL of oleylamine and 9 mL of toluene into a 20 mL beaker to form precursor solution B;

[0052] Step (2): 400 μL of precursor solution A was quickly added to 10 mL of precursor solution B, and the mixture was stirred for 30 minutes. After the reaction was completed, 20 mL of ethanol was quickly added, and then centrifuged at a speed of 5000 rpm. The lower layer of black solid was removed and stored for related performance tests.

[0053] Embodiment 2:

[0054] This embodiment is basically the same as embodiment 1, except that in step (1), 2 mmol of lead bromide is used instead of 2 mmol of lead chloride as a precursor.

[0055] Embodiment 3:

[0056] This embodiment is basically the same as embodiment 1, except that in step (1), 2 mmol lead iodide is used instead of 2 mmol lead chloride as a precursor.

[0057] See attached Figure 1 , which is the absorption spectrum of lead sulfide quantum dots prepared using lead chloride, lead bromide, and lead iodide as lead precursors provided in Examples 1-3, and the exciton absorption peaks of the obtained lead sulfide quantum dots are all in the range of 850-900nm.

[0058] See attached Figure 2 , is a transmission electron micrograph of the lead sulfide quantum dots provided in Example 2. In the transmission electron micrograph, all particles are independently dispersed, and the average diameter is about 3.47 nm. From the high-resolution transmission electron micrograph, lattice fringes with a spacing of 0.29 nm are seen, corresponding to the (111) crystal plane of lead sulfide (PDF#05-0592).

[0059] See attached Figure 3 , is the X-ray diffraction pattern of the lead sulfide quantum dots provided in Example 2. The diffraction peaks of the lead sulfide quantum dots are consistent with the peak positions of the standard diffraction pattern of lead sulfide (PDF#05-0592).

[0060] Embodiment 4:

[0061] This embodiment is basically the same as embodiment 2, except that the reaction time of step (2) is extended to 120 minutes.

[0062] See attached Figure 4 , which is the absorption spectrum of the lead sulfide quantum dots provided in Example 4 at different reaction times. As the reaction time increases, the absorption intensity of the lead sulfide quantum dot solution gradually increases, and the position of the exciton absorption peak gradually red-shifts. When the reaction time is 1, 15, 45, and 120 minutes, the band gap energies of the lead sulfide quantum dots are measured to be 1.50, 1.37, 1.30, and 1.26 eV, respectively. This shows that lead sulfide quantum dots with different band gaps can be obtained by controlling the reaction time.

[0063] Embodiment 5:

[0064] Step (1): Weigh 1 mmol of N,N'-di-n-butylthiourea and 2 mmol of lead bromide respectively, add them into 5 mL of N,N'-dimethylformamide, and stir thoroughly to form a precursor solution A;

[0065] Add 1 mL of oleylamine and 9 mL of toluene into a 20 mL beaker to form precursor solution B;

[0066] Step (2): 400 μL of precursor solution A was quickly added to 10 mL of precursor solution B, and the mixture was stirred for 30 minutes. After the reaction was completed, 20 mL of ethanol was quickly added, and then centrifuged at a speed of 5000 rpm. The lower layer of black solid was removed and stored for related performance tests.

[0067] Embodiment 6:

[0068] This example is basically the same as Example 5, except that in step (1), 1 mmol N,N'-di(4-methylphenyl)thiourea is used instead of 1 mmol N,N'-di-n-butylthiourea as a precursor.

[0069] See attached Figure 5 , which is the absorption spectrum of lead sulfide quantum dots prepared by using different chalcogen precursors provided in Examples 2 and 5-6. The chalcogen precursor used to prepare lead sulfide quantum dots is a thiourea derivative, and the substituents of the thiourea derivatives used in Examples 2 and 5-6 are different. Among them, the substituents of the thiourea derivatives used in Examples 2 and 6 are aromatic groups, and the substituents of the thiourea derivatives used in Example 5 are alkyl groups. When the substituents are aromatic groups, the reactivity of the thiourea derivatives is higher, and the absorption wavelength of the lead sulfide quantum dots prepared under the same conditions is redder. In addition, further introducing an electron-donating group, such as a methyl group (Example 6), into the aromatic group can further improve the reactivity of the thiourea derivatives, thereby red-shifting the absorption wavelength.

[0070] Embodiment 7:

[0071] Step (1): Weigh 1 mmol of lead bromide and 1 mmol of N,N'-diphenylthiourea, add them into 5 mL of N,N'-dimethylformamide, and stir thoroughly to form a precursor solution A;

[0072] Add 1 mL of oleylamine and 9 mL of toluene into a 20 mL beaker to form precursor solution B;

[0073] Step (2): 400 μL of precursor solution A was quickly added to 10 mL of precursor solution B, and stirring was continued for 30 minutes. After the reaction was completed, 20 mL of ethanol was quickly added, and the mixture was centrifuged at a speed of 5000 rpm. The lower layer of black solid was removed and stored for relevant performance tests.

[0074] Embodiment 8:

[0075] This embodiment is substantially the same as embodiment 7, except that in step (1), the amount of lead bromide is increased from 1 mmol to 3 mmol.

[0076] See attached Figure 6 , which is the absorption spectrum of lead sulfide quantum dots prepared by using lead bromide and N,N'-diphenylthiourea in different ratios as precursors provided in Examples 2, 7-8, the concentration of N,N'-diphenylthiourea is fixed at 0.2M, and the molar ratio of lead bromide to N,N'-diphenylthiourea is increased from 1:1 to 3:1. Within the above range, changing the precursor ratio has little effect on the band gap of lead sulfide quantum dots. Due to the limited solubility of lead bromide in N,N'-dimethylformamide, it is difficult to further increase the ratio.

[0077] Embodiment 9:

[0078] Step (1): Weigh 2 mmol of lead bromide and 1 mmol of N,N'-diphenylthiourea, add them into 10 mL of N,N'-dimethylformamide, and stir thoroughly to form a precursor solution A;

[0079] Add 1 mL of oleylamine and 9 mL of toluene into a 20 mL beaker to form precursor solution B;

[0080] Step (2): 400 μL of precursor solution A was quickly added to 10 mL of precursor solution B, and stirring was continued for 30 minutes. After the reaction was completed, 20 mL of ethanol was quickly added, and the mixture was centrifuged at a speed of 5000 rpm. The lower layer of black solid was removed and stored for relevant performance tests.

[0081] Embodiment 10:

[0082] This embodiment is basically the same as embodiment 9, except that in step (1), the concentration of N,N'-diphenylthiourea in the precursor solution A is increased from 0.1 M to 0.5 M, that is, 2 mmol of lead bromide and 1 mmol of N,N'-diphenylthiourea are weighed and added to 2 mL of N,N'-dimethylformamide, and stirred thoroughly to form precursor solution A.

[0083] See attached Figure 7 , which is an absorption spectrum of lead sulfide quantum dots prepared using different concentrations of N,N'-diphenylthiourea provided in Examples 2, 9-10. Other conditions in the above examples remain the same, and the concentration of N,N'-diphenylthiourea in the precursor solution A is 0.1M, 0.2M and 0.5M. As the concentration of the reactants in the precursor solution A increases, the absorption wavelength of the prepared lead sulfide quantum dots red-shifts.

[0084] Embodiment 11:

[0085] Step (1): Weigh 2 mmol of lead bromide and 1 mmol of N,N'-diphenylthiourea, add them into 5 mL of N,N'-dimethylformamide, and stir thoroughly to form a precursor solution A;

[0086] Add 2 mL of oleylamine and 8 mL of toluene into a beaker to form precursor solution B;

[0087] Step (2): 400 μL of precursor solution A was quickly added to 10 mL of precursor solution B, and stirring was continued for 30 minutes. After the reaction was completed, 20 mL of ethanol was quickly added, and the mixture was centrifuged at a speed of 5000 rpm. The lower layer of black solid was removed and stored for relevant performance tests.

[0088] Embodiment 12:

[0089] This example is substantially the same as Example 11, except that: in step (1), 3 mL of oleylamine and 7 mL of toluene are added to a beaker to form a precursor solution B;

[0090] Embodiment 13:

[0091] This example is substantially the same as Example 11, except that: in step (1), 5 mL of oleylamine and 5 mL of toluene are added to a beaker to form a precursor solution B;

[0092] Embodiment 14:

[0093] This example is substantially the same as Example 11, except that: in step (1), 10 mL of oleylamine is added to the beaker as precursor solution B;

[0094] See attached Figure 8, which is an absorption spectrum of lead sulfide quantum dots prepared using different volume fractions of oleylamine solution as precursor solution B provided in Examples 2 and 11-14. The volume fraction of oleylamine in the toluene solution is increased from 10% to 100%, 100% being pure oleylamine as precursor solution B. As the volume fraction of oleylamine increases, the absorption wavelength of the prepared lead sulfide quantum dots red-shifts.

[0095] Embodiment 15:

[0096] Preparation of lead sulfide quantum dots co-coordinated by oleic acid and halogen via ligand exchange.

[0097] Step (1): Weigh 2 mmol of lead bromide and 1 mmol of N,N'-diphenylthiourea, add them into 5 mL of N,N'-dimethylformamide, and stir thoroughly to form a precursor solution A;

[0098] Add 1 mL of oleylamine and 9 mL of toluene into a 20 mL beaker to form precursor solution B;

[0099] Step (2): 400 μL of precursor solution A was quickly added to 10 mL of precursor solution B, and stirring was continued for 30 minutes. After the reaction was completed, 20 mL of ethanol was quickly added, and the mixture was centrifuged at a speed of 5000 rpm. The lower layer of black solid was removed and stored for relevant performance tests.

[0100] Step (3): Add 1 mL of oleic acid and 5 mL of n-hexane to the lower solid separated in step (2) and stir rapidly to mix, let stand at room temperature for 6 hours, add 20 mL of ethanol, separate by centrifugation, remove the lower black solid, store the black solid and perform relevant performance tests.

[0101] The lower black solid obtained in step (2) is lead sulfide quantum dots coordinated by oleylamine and halogen, and the PLQY of the lead sulfide quantum dots is low, about 4%. After the ligand exchange in step (3), the lower black solid obtained is lead sulfide quantum dots coordinated by oleic acid and halogen, and its PLQY is increased to 45%.

[0102] See attached Fig. 9 , which are absorption and emission spectra of lead sulfide quantum dots before and after ligand exchange provided in Example 15. The absorption and emission spectra of the lead sulfide quantum dots after ligand exchange are both red-shifted compared to those before ligand exchange. At the same time, the PLQY of the lead sulfide quantum dots after ligand exchange is significantly improved.

[0103] Embodiment 16:

[0104] Preparation of lead selenide quantum dots.

[0105] Step (1): weigh 2 mmol of lead bromide and 1 mmol of N,N'-dibutylselenourea, add them into 5 mL of N,N'-dimethylformamide, and stir thoroughly to form a precursor solution A;

[0106] Add 1 mL of oleylamine and 9 mL of toluene into a 20 mL beaker to form precursor solution B;

[0107] Step (2): 400 μL of precursor solution A was quickly added to 10 mL of precursor solution B, and the mixture was stirred for 30 minutes. After the reaction was completed, 20 mL of ethanol was quickly added, and then centrifuged at a speed of 5000 rpm. The lower layer of black solid was removed and stored for related performance tests.

[0108] Step (3): Add 1 mL of oleic acid and 5 mL of n-hexane to the lower solid separated in step (2) and stir rapidly to mix, let stand at room temperature for 6 hours, add 20 mL of ethanol, separate by centrifugation, remove the lower black solid, store the black solid and perform relevant performance tests.

[0109] See attached Fig.10 , is an absorption spectrum of the lead selenide quantum dots provided in Example 16. The chalcogenide precursor used in preparing the lead selenide quantum dots is selenourea and its derivatives.

[0110] Embodiment 17:

[0111] This example is basically the same as Example 16, except that: the amount of all raw materials and solvents used in the reaction is increased by 3 times (solid by mass, liquid by volume), that is, in step (1), 6 mmol lead bromide and 3 mmol N,N'-dibutylselenourea are added to 15 mL N,N'-dimethylformamide and stirred thoroughly to form a precursor solution A; 3 mL oleylamine and 27 mL toluene are added to a beaker to form a precursor solution B;

[0112] Step (2): 1200 μL of precursor solution A was quickly added to 30 mL of precursor solution B, and the mixture was stirred for 30 minutes. After the reaction was completed, 60 mL of ethanol was quickly added, and then centrifuged at a speed of 5000 rpm. The lower layer of black solid was removed and stored for related performance tests.

[0113] Step (3): Add 3 mL of oleic acid and 15 mL of n-hexane to the lower solid separated in step (2) and stir rapidly to mix, let stand at room temperature for 6 hours, add 60 mL of ethanol, separate by centrifugation, remove the lower black solid, store the black solid and perform relevant performance tests.

[0114] Embodiment 18:

[0115] This example is basically the same as Example 16, except that the amount of all raw materials and solvents used in the reaction is increased to 5 times (solids by mass, liquids by volume).

[0116] Embodiment 19:

[0117] This example is basically the same as Example 16, except that the amount of all raw materials and solvents used in the reaction is increased by 12 times (solids by mass, liquids by volume).

[0118] Embodiment 20:

[0119] This example is basically the same as Example 16, except that the amount of all raw materials and solvents used in the reaction is increased by 35 times (solids by mass, liquids by volume).

[0120] See attached Fig.11 , which is a photo of the lead sulfide quantum dot enlarged reaction provided in Examples 16-20. The preparation scale can be expanded by simply proportionally increasing the amounts of all reactants and solvents in Example 16. In the reaction of Example 20, 1.92 g of lead sulfide quantum dots can be obtained in a single reaction.

[0121] See attached Fig.12 a, absorption and emission spectra of lead sulfide quantum dots prepared by different scale amplification reactions provided in Examples 16 to 20. The absorption and emission spectra of lead sulfide quantum dots prepared by different scale amplification reactions are consistent.

[0122] See attached Fig.12 b, the absorption peak, emission peak and PLQY value of the lead sulfide quantum dots provided in Examples 16 to 20. The photophysical properties of the lead sulfide quantum dots prepared by the amplification reactions of different scales are basically the same.

[0123] Embodiment 21:

[0124] This embodiment provides a method for preparing a light-emitting device based on the lead sulfide quantum dots prepared by the present invention.

[0125] The lead sulfide quantum dots prepared in Example 16 were dispersed in n-hexane at a concentration of 10 mg mL -1. Take another 1g of polydimethylsiloxane and 20mg of SBA-15 molecular sieve (pore size 6-7nm) and add them to 1mL of lead sulfide quantum dot solution. After vigorous stirring, ultrasonicate for 10 minutes to ensure sufficient mixing, then keep the container open and continue stirring for 1 hour until the n-hexane is completely evaporated. Finally, the mixture of quantum dots, molecular sieves and polymers is injected into molds of different shapes, moved to an oven and kept at 60°C for 1 hour until completely cured, to obtain quantum dot / molecular sieve / polymer complexes of different shapes. Among them, the mixture of quantum dots, molecular sieves and polymers is injected into the hemispherical lens of the LED chip, and after it is cured, it is combined with the LED chip to prepare a QD-LED device, whose structure is as shown in the attached figure. Fig.13 .

[0126] See attached Fig.14 a, is a graph showing the change in the luminescence spectrum of the near-infrared QD-LED device provided in Example 21 as the current increases. The luminescence peak position and peak shape of the device do not change as the current increases.

[0127] See attached Fig.14 b, the optical power of blue light, near infrared light and the sum of the two of the near infrared QD-LED device provided in Example 21 changes with the increase of current, the blue light comes from the LED chip, and the near infrared light comes from the lead sulfide quantum dots. At a current of 160mA, the optical power of the near infrared light reaches 8.0mW. After Gaussian fitting is used to supplement the luminescence spectrum that is not detected by the detector with a wavelength greater than 1050nm, the actual optical power reaches 9.2mW, which is comparable to the near infrared optical power (~10mW) of the current InGaAs-based III-V LED.

[0128] Although the present invention has been described in conjunction with the embodiments, the present invention is not limited to the above embodiments. It should be understood that under the guidance of the concept of the present invention, those skilled in the art may make various modifications and improvements. The appended claims summarize the scope of the present invention.

Claims

1. A method for preparing a lead chalcogenide quantum dot material, characterized in that: Use the following procedure at room temperature: (1) Preparation of precursor: Dissolve lead halide and chalcogen precursor in N,N'-dimethylformamide, and form precursor solution A after sufficient stirring; The chalcogenide precursor has a structure as shown in Formula A: In formula A, E is selected from one of sulfur and selenium; R1, R2, R3, and R4 are independently selected from one of hydrogen, substituted or unsubstituted C1-C20 alkyl, and substituted or unsubstituted C6-C60 aryl; and the substituted substituent is selected from one of halogen, C1-C10 alkyl, and C1-C10 alkoxy; Oleylamine and toluene are mixed and stirred sufficiently to form a precursor solution B, or oleylamine is directly used as the precursor solution B. (2) Preparation of lead sulfide quantum dots: The precursor solution A is quickly added to the precursor solution B, and the solution is kept stirred vigorously. The reaction time is 5-120 minutes. After the reaction is completed, an excess of ethanol is added, and the solid is separated and purified to obtain the lead sulfide quantum dots coordinated by oleylamine and halogen. (3) Ligand exchange: Add oleic acid and n-hexane to the lower solid obtained in step (2), stir and mix quickly, let stand at room temperature for 6-12 hours, separate and purify, and obtain lead sulfide quantum dots coordinated by oleic acid and halogen.

2. The method for preparing the lead chalcogenide quantum dot material according to claim 1, characterized in that: The lead halide described in step (1) is selected from lead chloride, lead bromide or lead iodide; Preferably, the lead halide is lead bromide.

3. The method for preparing the lead chalcogenide quantum dot material according to claim 1, characterized in that: In step (1), in the structure of formula A of the chalcogenide precursor, two of R1, R2, R3, and R4 are selected from hydrogen; Preferably, at least one of R1 and R2 is selected from substituted or unsubstituted C6-C60 aryl, at least one of R3 and R4 is selected from substituted or unsubstituted C6-C60 aryl, and the substituted substituent is selected from one of halogen, C1-C10 alkyl, and C1-C10 alkoxy; More preferably, one of R1 and R2 is selected from substituted or unsubstituted C6-C60 aryl, and the other is selected from hydrogen, one of R3 and R4 is selected from substituted or unsubstituted C6-C60 aryl, and the other is selected from hydrogen, and the substituted substituent is selected from one of halogen, C1-C10 alkyl, and C1-C10 alkoxy; More preferably, R1 and R3 are C6-C60 aromatic groups, and R2 and R4 are hydrogen atoms.

4. The method for preparing the lead chalcogenide quantum dot material according to claim 1, characterized in that: The sulfide precursor in step (1) is selected from N,N'-diphenylthiourea, N,N'-di-n-butylthiourea, N,N'-di(4-methylphenyl)thiourea, selenourea, and N,N'-dibutylselenourea. Preferably, the sulfide precursor in step (1) is selected from N,N'-diphenylthiourea.

5. The method for preparing the lead chalcogenide quantum dot material according to claim 1, characterized in that: In step (1), the molar ratio of lead halide to chalcogen precursor is 1:1 to 3:

1.

6. The method for preparing the lead chalcogenide quantum dot material according to claim 1, characterized in that: In step (1), the concentration of the chalcogen precursor in the precursor solution A is 0.05M to 0.5M, preferably, the concentration is 0.1M to 0.3M.

7. The method for preparing lead chalcogenide quantum dot material according to claim 1, characterized in that: In step (1), the volume fraction of oleylamine in the precursor solution B is 5% to 100%.

8. The method for preparing lead chalcogenide quantum dot material according to claim 1, characterized in that: The volume fraction of oleic acid in the n-hexane solution in step (3) is 10% to 30%.

9. The method for preparing the lead chalcogenide quantum dot material according to claim 1, characterized in that: In step (1), lead bromide and N,N'-diphenylthiourea in a molar ratio of 2:1 are dissolved in N,N'-dimethylformamide to form a precursor solution A, wherein the concentration of N,N'-diphenylthiourea is 0.2 M; In step (1), oleylamine and toluene are mixed to form a precursor solution B, wherein the volume fraction of oleylamine in the precursor solution B is 10%; In step (2), the precursor solution A is quickly mixed with the precursor solution B in a volume ratio of 1:25, and the solution is kept vigorously stirred. After reacting for 30 minutes, the reaction is terminated with an excess of ethanol, and the supernatant is removed after separation and purification. The lower layer solid obtained is lead sulfide quantum dots coordinated by oleylamine and halogen; In step (3), oleic acid and n-hexane are added to the obtained lower solid layer and the mixture is quickly stirred and mixed, and the mixture is allowed to stand at room temperature for 6 hours, and then separated and purified to obtain lead sulfide quantum dots coordinated by oleic acid and halogen.

10. The method for preparing the lead chalcogenide quantum dot material according to claim 1, characterized in that: In step (1), lead bromide and N,N'-dibutylselenourea in a molar ratio of 2:1 are dissolved in N,N'-dimethylformamide to form a precursor solution A, wherein the concentration of N,N'-dibutylselenourea is 0.2 M; In step (1), oleylamine and toluene are mixed to form a precursor solution B, wherein the volume fraction of oleylamine in the precursor solution B is 10%; In step (2), the precursor solution A is quickly mixed with the precursor solution B in a volume ratio of 1:25, and the solution is kept vigorously stirred. After reacting for 30 minutes, the reaction is terminated with an excess of ethanol, and the supernatant is removed after separation and purification. The lower layer solid obtained is lead selenide quantum dots coordinated by oleylamine and halogen; In step (3), oleic acid and n-hexane are added to the obtained lower solid layer and mixed rapidly, and the mixture is allowed to stand at room temperature for 6 hours, and separated and purified to obtain lead selenide quantum dots coordinated by oleic acid and halogen.

11. A lead chalcogenide quantum dot material, comprising lead sulfide quantum dots and lead selenide quantum dots, obtained by the preparation method according to claim 1.

12. Use of the lead sulfide quantum dot material according to claim 11, wherein the lead sulfide quantum dot material is used in a light-emitting device.

Images